An electrophotographic imager includes a photoconductive element, a charger, and a light source to expose areas of a charged surface of the photoconductive element to form a latent image. A development element is coupled relative to the photoconductive element to develop, via charged marking agent, the latent image on the photoconductive element. An exposure adjustment factor is selectively applied, prior to the exposing, to a first printable area of the latent image.
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12. An electrophotographic imager control portion comprising:
a processor, in association with instructions stored in a memory, to selectively apply an exposure adjustment factor on a photoconductive element at a first printable portion of a latent image on the photoconductive element,
wherein a decision whether to apply, and a magnitude of, the exposure adjustment factor is based on an image-dependent marking agent transfer demand regarding a first evaluation portion of the latent image preceding the first printable portion and a development state of a first development portion of a development element associated corresponding to the first evaluation portion,
wherein the marking agent transfer demand indicates the volume of marking agent to be transferred via development of the first evaluation portion of the latent image, the volume of marking agent based on a pixel density parameter of a printable portion of the latent image,
and wherein the development state of the development element is based on a location on the development element with respect to the volume of the charged marking agent and with respect to an age since last development usage at the location on the development element.
1. An electrophotographic imager comprising:
a photoconductive element;
a charger to charge a surface of the photoconductive element;
a light source to expose areas of the charged surface to form a latent image;
a development element coupled relative to the photoconductive element to develop, via charged marking agent, the latent image on the photoconductive element; and
a controller to selectively apply an exposure adjustment factor to a first printable area of the latent image, wherein a magnitude of the exposure adjustment factor is based on a marking agent transfer demand regarding a first evaluation portion of the latent image preceding the first printable area and on a development state of the development element for the first evaluation portion,
wherein the marking agent transfer demand indicates the volume of marking agent to be transferred via development of the first evaluation portion of the latent image, the volume of marking agent based on a pixel density parameter of a printable portion of the latent image,
and wherein the development state of the development element is based on a location on the development element with respect to the volume of the charged marking agent and with respect to an age since last development usage at the location on the development element.
18. A method of manufacturing an electrophotographic imager comprising:
arranging a light source to expose areas of a chargeable surface of a photoconductive element to form a latent image, including arranging the light source to be controllable to selectively apply a first exposure adjustment factor to a first printable portion of the latent image and to selectively apply at least one second exposure adjustment factor to at least one subsequent printable portion of the latent image; and
arranging a development element to be coupled relative to the photoconductive element to develop the latent image on the photoconductive element with a marking agent, wherein the respective first and second exposure adjustment factors are based at least on a magnitude of a pixel density of a first evaluation portion of the latent image preceding the first printable area and a development state of the development element,
wherein the marking agent transfer demand indicates the volume of marking agent to be transferred via development of the first evaluation portion of the latent image, the volume of marking agent based on a pixel density parameter of a printable portion of the latent image,
and wherein the development state of the development element is based on a location on the development element with respect to the volume of the charged marking agent and with respect to an age since last development usage at the location o the development element.
2. The electrophotographic imager of
3. The electrophotographic imager of
4. The electrophotographic imager of
5. The electrophotographic imager of
6. The electrophotographic imager of
wherein each different printable area corresponds to a respective non-developed area of a plurality of non-developed areas of the development element.
7. The electrophotographic imager of
8. The electrophotographic imager of
9. The electrophotographic imager of
10. The electrophotographic imager of
11. The electrophotographic imager of
13. The electrophotographic imager control portion of
14. The electrophotographic imager control portion of
a non-printable portion with the first development portion having a development state in which no development has occurred for a number of development cycles of the development element; and
a printable portion for which the marking agent transfer demand exceeds a threshold.
15. The electrophotographic imager control portion of
16. The electrophotographic imager control portion of
17. The electrophotographic imager control portion of
19. The method of
20. The method of
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Digital electrophotographic imaging has already revolutionized document production. Yet, ever faster processing and higher volumes of imaging continue to pose challenges in achieving high quality images on printed documents.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise.
At least some examples of the present disclosure provide for performing electrophotographic imaging with reduced ghosting effects by employing an exposure adjustment factor. In some examples, such ghosting effects refer to an unintentional duplication of a portion of an image appearing within other portions of the same image.
In some examples, the exposure adjustment factor is selectively applied to a first printable area of the latent image, wherein the magnitude of the exposure adjustment factor is based at least on a marking agent transfer demand regarding a first evaluation portion of the latent image preceding the first printable area and on a development state of the developer element for the first evaluation portion. In some examples, the first evaluation portion immediately precedes the first printable area.
In some examples, the term “marking agent transfer demand” refers to an absolute or relative amount of marking agent to be transferred from the development element to the photoconductive element to achieve the intended amount of development of the latent image via the marking agent.
In some examples, an exposure adjustment factor refers to intentionally increasing or decreasing exposure of a portion of a latent image on a photoconductive element in addition to or after the electrophotographic imager makes it exposure calculation according to its normal operating procedures. In some examples, a magnitude of the exposure adjustment factor may be expressed via a percentage, such as percentage increase (e.g. 1%, 2%, 3%, 4%, 5%, 10%, etc.) in exposure above a nominal value for a given pixel or area according to the normal operating procedures or a percentage decrease (e.g. −1%, −2%, −3%, −4%, −5%, −10%, etc.) in exposure below the nominal value for a given pixel or area according to the normal operating procedures.
In some examples, the term “first” does not necessarily refer to an initial instance of a printable portion of the entire latent image or the first instance of an evaluation portion of the entire latent image, but rather the term “first” refers to portion of interest within the latent image for which adjustment may be applied. In some instances, the terms “portion” and “area” may be used interchangeable throughout the present disclosure without intending any substantive difference between the two terms.
In some examples, the first evaluation portion of the latent image comprises a second printable area of the latent image and the marking agent transfer demand is indicative of at least a pixel density of second printable area relative to a threshold.
In some examples, the first evaluation portion of the latent image comprises a non-printable area of the latent image, which also corresponds to at least one portion of the development element which has not been used for development for a prolonged period of time. In some examples, such prolonged non-development is expressed as a number of development cycles of the development element for which the non-development has occurred.
In some examples, prior to exposing the photoconductive element via a light source, the exposure adjustment factor is applied selectively to increase the amount of exposure (i.e. cause over-exposure) to thereby increase the degree of development of portions of an image that would otherwise be underdeveloped due to a relative marking agent transfer demand and/or the relative development state of at least some portions of the developer element.
In some examples, prior to exposing the photoconductive element via a light source, the exposure adjustment factor is applied selectively to decrease the amount of exposure to decrease the degree of development (i.e. to underdevelop) of portions of an image expected to develop within a target range, which in turn provides an overall compensation pattern to compensate for portions of an image expected to be underdeveloped due to the relative marking agent transfer demand and/or the relative development state of at least some portions of the development element.
In some examples, a combination of both of the previously described examples is employed to minimize unintentional underdevelopment and/or ghosting effects. For instance, some portions of an image which are expected to be underdeveloped will be purposely overexposed and some portions of the same image which are expected to be normally developed will be purposely underexposed.
In some examples, a decision whether to apply an exposure adjustment factor, and a magnitude of the exposure adjustment factor, is at least partially based on a difference between a marking agent transfer demand of the first printable area and a subsequent printable area.
In some examples, employment of the exposure adjustment factor is performed without otherwise altering the bias voltages of the developer and/or of the photoconductive element during an interpage gap interval, which would otherwise result in wasted marking agent and increased operating costs. In addition, in arrangements in which an interpage gap interval of the photoconductive element is relatively small, the selective application of the exposure adjustment factor (in accordance with some examples of the present disclosure) may be performed successfully whereas insufficient time may not be available to attempt correction via purging excess marking agent by altering the bias voltages of the development element and/or photoconductive element.
In some examples, employment of the exposure adjustment factor may account for and minimize the phenomenon of excessive marking agent charging and/or of unintentional undercharging regardless of where it might occur on an image to be printed. For instance, the selective application of the exposure adjustment factor can minimize unintentional underdevelopment and/or ghosting in a midportion of a printed image and is not limited to minimizing unintentional underdevelopment at the start of a printed page.
These examples, and additional examples, are described throughout the present disclosure in association with at least
A development element 33 is coupled relative to the photoconductive element 30 to develop the latent image into a developed image for later transfer onto a media. However, prior to writing the image onto the photoconductive element 30, via a controller 20 the imager 10 employs a selective exposure adjustment factor 24 to modify the extent to which the light source 22 exposes select portions of the charged photoconductive element 30. In some examples, the location and magnitude of this modification is at least partially based on the extent to which at least some portions of the development element 33 have not been developed for a period of time and/or on an image-dependent marking agent transfer demand. In some examples, when used in association with the term “marking agent transfer demand”, the term “image dependent” means that the absolute or relative amount of marking agent intended to be transferred (from the development element to the photoconductive element) depends on the particular image (or portion of the image) being developed. Further details regarding this arrangement are further described later in association with at least
As shown in
In some examples, imager 21 includes a control portion 28 to direct general operations of imager 21 and/or to implement the exposure adjustment factor 24 of
While not shown in
In preparation to receive an image, as further shown in
While not shown in
In one aspect, the development element 33 electrically charges marking agent by friction via a tribo-charging process that is generally continuous during a printing process. In some instances, if a development element 33 is cycled (e.g. a roller is rotated) for relatively long periods of time without developing latent images, then the marking agent within the developer 32 at development element 33 can become excessively charged which makes it difficult to develop or transfer the marking agent (distributed on the surface of the development element 33) onto the photoconductive element 30. This behavior, in turn, makes the initial marking agent image formed on the photoconductive element 30 lighter in appearance than desired. In other words, the initial marking agent image is underdeveloped. After an area has been initially developed on the photoconductive element 30, the subsequent marking agent available at the development element 33 has lower amounts of electrical charge and is therefore easier to develop (i.e. transfer) onto the photoconductive element 30 so that the subsequently developed areas on the photoconductive element 30 appear darker, i.e. they develop closer to the intended darkness. This underdevelopment effect can happen anywhere on the printed page following long continuous runs of portions of a development element 33 without marking agent development, which in turn permits the marking agent on the development element 33 to become excessively charged. Moreover, after initial depletion of the excessively charged marking agent, the overcharging effect builds up again in a linear fashion as the development element 33 cycles until portions of the development element 33 are used again for development. At least some aspects of this phenomenon are illustrated in association with at least
In some instances, upon a placing a relatively high demand of marking agent transfer (i.e. marking agent transfer demand) upon the development element 33 for a relative high pixel density region of a latent image, the relative amount of charge for marking agent on the development element 33 becomes significantly diminished such that the marking agent may be considered to be undercharged. With this undercharged marking agent condition, upon performing development of portions of the latent image subsequent to the high density pixel region, the subsequent portions may be overdeveloped due to excess marking agent transferring onto the photoconductive element. At least some aspects of this phenomenon are illustrated in association with at least
In one example, image 105 would be formed onto media by employing one of the electrophotographic imagers of
It will be understood that image 105 may include many different combinations and configurations of printable (P) portions and non-printable (NP) portions, and therefore image 105 in
In the example shown in
Column 102 includes printed portion (P) extending throughout a full length of column 102, while column 103 includes a non-printed portion 104 for a significant extent, which is then followed by a printed portion 106. Column 110 includes printed portion 112, non-printed portion 114, and printed portion 116. In one aspect, the respective printed and non-printed portions are not strictly limited to rectangular shapes but may have any desired shape or size. Similarly, column 120 includes multiple printed portions 122, 126, 140 and non-printed portions 124, 130 interposed therein.
As just one illustrative example, the respective printed and non-printed portions of column 120 are arranged in series along the direction of media travel during an imaging process.
As can be seen from
Via the juxtaposition of image 105 relative to array 160 of maps 162A-162K, diagram 100 of
In the particular example shown in
In at least some examples of the present disclosure, each respective map 162A-162K corresponds to the surface area of one cycle of the development element 33 and each map is employed to track pixels of the image 105 relative to a development state of the development element 33. As previously noted, in some examples the development element 33 has a surface area roughly 1/11th of the printed image 105. For purposes of mapping areas of the development element 33 where excessively charged marking agent resides, in some examples, a resolution of 75 dpi×75 dpi is employed. Assuming that 4 bits per “development element pixel” are used, a 32 kbyte memory buffer would be sufficient to map the development element 33 for keeping track of areas with excessively charged marking agent or with undercharged marking agent. Accordingly, by tracking pixels on the development element 33 one cycle at a time, a relatively small and manageable memory buffer may be employed to track excessively charged marking agent or undercharged marking agent on the development element 33.
In some examples, the memory buffer resides in a developer memory 170, as shown in
In contrast, a full greyscale bit map of the entire image 105 (e.g. raster image) would involve a much larger memory source to track pixels regarding excessively charged marking agent. For example, for an image measuring 8.5″×11″ at 1200 dpi×600 dpi printed resolution with 8 bits per YMCK pixel, the memory source would be 254 Mbytes (e.g. 64 Mbyte/color) per page.
Accordingly, by tracking charged marking agent via pixels corresponding to the physical size of the development element 33, a much smaller memory may be employed than would otherwise be involved if “charged marking agent” pixel tracking occurred for a given full size image.
In some examples, image 105 is larger or smaller than a U.S. Letter size document and/or development element 33 has a surface area other than 1/11th of the image 105. Accordingly, when development element 33 comprises a roller, it may have a circumference other than one inch.
In some examples, portion 182A corresponds to a column or elongate portion of a larger image, such as but not limited to a full width page image. In one such example, portion 182A corresponds to column 103 in image 105 in
In some examples, the height (H2) of each segment 184A corresponds to a surface for one cycle of the development element 33, which is represented by H1 in
In some examples, at least the last non-print segment 184A before segment 188A comprises a first evaluation portion. In some instances, it is referred to as a first evaluation portion because it may be evaluated with respect to marking agent transfer demand and/or a development state of a development portion of the development element corresponding to the first evaluation portion. In some instances, this information regarding the first evaluation portion is used to determine whether to apply, and a magnitude of, an exposure adjustment factor for the first printable area (e.g. print segment 188A) that follows the first evaluation portion. In some examples, the first printable area immediately follows the first evaluation portion. As previously noted, in some examples the magnitude of the exposure adjustment factor is expressed or implemented as a percentage (e.g. 1%, 2%, 5%, 10%, etc.) of increased exposure (relative to a nominal target exposure per normal operating procedures) to compensate for the expected underdevelopment of the particular portions of the latent image.
In some instances, the non-print segments 184A can be viewed as an area having a pixel density of zero, and therefore a marking agent transfer demand of zero.
In this scenario of prolonged non-development, if the intended image portion 182A were actually printed without exposure adjustment, then portion 182B in
As represented by relatively denser cross-hatching in
While not shown in
In some examples, just one underdeveloped segment 188B in image portion 182B is present without a second underdeveloped segment 189B. This situation may arise where the non-development of a portion (e.g. portion 184C) of the development roller 33 is not as severe and/or where the high pixel density region 186A of the intended image portion 182A is less dense.
It will be understood that, in at least some examples, the high pixel density regions are involved in this phenomenon because of the relatively high degree of charge in those regions, which in turn place a higher demand on charged marking agent from the development element 33.
In some examples, a relative pixel density of a printable portion of an image refers to a pixel density being relatively higher or lower than a nominal pixel density for a latent image.
At least some examples of the present disclosure overcome the phenomenon that would be exhibited by underdeveloped portion 182B via selectively applying an exposure adjustment factor 24 (
When such exposure adjustment is implemented according to at least some examples of the present disclosure, then the underdeveloped printed segments 188B, 189B are avoided and instead the intended image portion 182A is realized in which segments 188A, 189A of high pixel density region 186A will exhibit their expected appearance or a reasonably close approximation thereof.
Further details regarding the manner in which this adjustment is implemented are described in association with the exposure adjustment manager 300 of
In some examples, portion 252A corresponds to a column (e.g. elongate portion) of a larger image, such as but not limited to a full width page image. In one such example, portion 252A corresponds to one of the columns in image 105 in
In this scenario, if the intended image portion 252A were actually printed without exposure adjustment, then portion 2523 in
In some examples, at least 268A comprises a first evaluation portion. In some instances, it is referred to as a first evaluation portion because it may be evaluated with respect to marking agent transfer demand and/or a development state of a development portion of the development element corresponding to the first evaluation portion. In some instances, this information regarding the first evaluation portion is used to determine whether to apply, and a magnitude of, an exposure adjustment factor for the following segment 269A (e.g. a first printable area).
The situation illustrated in
While not shown in
Assuming that just one segment 269B exhibits overdevelopment, then subsequent segments such as segment 270B may exhibit the intended development, as represented by the nominal degree of cross-hatching shown for segments 254B, 270B, etc. This behavior provides an indication that the portion of the development element 33 has returned toward a normal operating range regarding the amount of charged marking agent carried by the development element 33.
While not shown in
It will be understood that, in at least some examples, the high pixel density regions are involved in this phenomenon because of the relatively high degree of charge used in those regions for development, which in turn place a higher demand on charged marking agent from the development element 33.
At least some examples of the present disclosure overcome the phenomenon that would be exhibited by overdeveloped portion 252B via selectively applying an exposure adjustment factor 24 (
When such exposure adjustment is implemented according to at least some examples of the present disclosure, then the overdeveloped printed segment 252B is avoided and instead the intended image portion 252A is realized in which segment 269A following high pixel density segment 268A will exhibit their expected appearance or a reasonably close approximation thereof.
Further details regarding the manner in which this adjustment is implemented are described in association with the exposure adjustment manager 300 of
In general terms, the exposure adjustment manager 330 operates to provide selective adjustment of exposure of a photoconductive element (30 in
As shown in
In some examples, in general terms the image map module 310 provides a map of an image to be developed and printed. As shown in
In some examples, image map module 310 comprises a marking agent transfer demand factor 325 to determine and/or indicate a relative degree of marking agent transfer demand for a particular portion of an intended image. For instance, a high pixel density region may place a relatively high demand on a volume of marking agent to be transferred via development from development element 33 for a given cycle of development element 33. In some examples, the marking agent transfer demand factor 325 is associated with and/or utilizes the pixel density parameter 324 to make its determination.
In some examples, via parameters 316, 318, 320, a user may determine the size, shape, and/or type of the printable portions and non-printable portions to be tracked. In some examples, the size, shape, and/or type of the printable portions and non-printable portions are automatically determined based on the pixel density parameter 322 and/or darkness parameter 324.
In some examples, the development map module 330 generally operates to determine a relative degree of marking agent charge on the development element 33 during a continuous imaging process, which generally corresponds to a relative degree of development of charged marking agent onto photoconductive element 30.
As shown in
In some examples, the development map module 330 comprises a marking agent transferability parameter 344 to determine and/or indicate the extent to which marking agent can be transferred (e.g. developed upon photoconductive element 30) at a volume or rate within a target operating range. In some examples, the marking agent transferability parameter 344 is at least partially based on an available volume of charged marking agent, and its degree of charge, across a surface of development element 33. Accordingly, in some examples, the marking agent transferability parameter 344 may act as an indicator of the relative overcharging or relative undercharging of marking agent on the development element 33. In some examples, a value of the marking agent transferability parameter 344 may be evaluated relative to a target operating range of at least the development element 33.
In some examples, in general terms the adjustment factor module 350 operates to determine and implement adjustments in the degree of exposure (of light source 22) to photoconductive element 30 to compensate for relatively overcharged marking agent, which may be due to prolonged periods of non-development for some portions of a development element 33 (
As shown in
In some examples, the initial development parameter 352 stores a value corresponding to the relative degree of exposure adjustment to occur for a printable segment to be initially developed after a prolonged period of non-development of the development element 33 for the particular portion of the development element 33 as in the example of
Meanwhile, the subsequent development parameter 354 stores a value corresponding to the relative degree of exposure adjustment to occur for each subsequent printable segment(s) following the initial printable segment. In some examples, the stored value of exposure adjustment per the subsequent development parameter 354 is generally less than the value of the exposure adjustment per the initial development parameter 352, and in some instances, may be expressed as a fraction.
In some examples, the value of the exposure adjustment (per the subsequent development parameter 354) decreases in magnitude for each subsequent development.
In some examples, at least some subsequent exposure adjustments are greater in magnitude than the initial exposure adjustment.
In some examples, the subsequent development parameter 354 comprises a constant parameter 356 and a variable parameter 358. The constant parameter 356 maintains a constant magnitude of exposure adjustment to subsequent development instances regardless of how many subsequent development instances follow the initial development instance. The variable parameter 358 varies the magnitude of exposure adjustment to decrease in magnitude with each successive subsequent instance of development. In some examples, the variable parameter 358 operates according to a limit of a number of times (e.g. 2, 3, 4, etc.) the exposure adjustment will be applied to subsequent development instances.
In some examples, the image threshold parameter 360 provides a mechanism to select and track a threshold of pixel density (parameter 322) for which application of the exposure adjustment factor will be triggered. In particular, as an image is prepared for exposure onto the photoconductive element 30, it will be determined what the pixel density would be in a given area of the image, and if the intended pixel density exceeds a threshold and if other conditions warrant (e.g. development state of development element), then an exposure adjustment factor is applied. Conversely, when the intended pixel density of the image in a particular region is less than the threshold, then no exposure adjustment factor is applied.
It will be understood that in some examples at least the size and/or shape parameters 316, 318 regarding an image are employed to determine the size and/or shape of regions to which the image threshold per parameter 360 is applied.
In some examples, the development threshold parameter 360 provides a mechanism to select and track a threshold of non-development (parameter 362) of portions of development element 33 for which application of the exposure adjustment factor will be triggered. In particular, in some examples as an image is prepared for exposure onto the photoconductive element 30, the development state for portions of the development element 33 is determined for any high pixel density regions of the image (those exceeding the image threshold per parameter 360), and if the determined development state exceeds a threshold per parameter 362, then an exposure adjustment factor is applied. Conversely, in some examples, when the determined development state of the development element 33 in a particular region is less than the threshold 362, then no exposure adjustment factor is applied regardless of whether a corresponding portion of the image has a high pixel density or not.
It will be understood that in some examples at least the size and/or shape parameters 340, 342 regarding an area of non-development are employed to determine the size and/or shape of regions to which the development threshold parameter 362 may be applied. It will be further understood that in some examples, at least the size and/or shape parameters regarding an area of undercharged marking agent are employed to determine the size and/or shape of regions to which the development threshold parameter 362 may be applied.
In some examples, the development threshold parameter 362 employs a threshold at least partially based on a number of cycles of the development element 33 for which non-development has occurred for at least one portion of the development element 33. In some examples, the number of cycles is associated with or correlated with the age parameter 336 of the development state per state function 332.
In some examples, the development threshold parameter 362 employs a threshold at least partially based on a measurable charge field on the development element 33 or an elapsed time since the last development (in the particular region of interest for the development element 33).
In some examples, whether the exposure adjustment factor applied will depend on a recharge interval parameter 364 and/or recharge rate 366 (
In some examples, information regarding the recharge rate and/or recharge interval can affect whether overdevelopment may occur following a high pixel density region of an intended image, and therefore can at least partially determine whether a selective exposure adjustment factor may be applied.
The recharge rate parameter 364 tracks the speed (e.g. how quickly) at which the development element 33 is recharged each time that re-charging occurs. In particular, in situations in which the recharge rate is low enough or less than a rate threshold, then underdevelopment and/or ghosting due to prolonged non-development of the development element 33 likely will not occur. Therefore, in these situations, an exposure adjustment factor will not be applied. However, where the recharge rate is high enough to exceed a threshold to create situations in which such underdevelopment and/or ghosting would be more likely to occur, then an exposure adjustment factor will be applied.
In some examples, the recharge interval parameter 364 and/or recharge rate 366 are not subject to modification. In some examples, these parameters 364, 366 may be modified via exposure adjustment manager 300 in order to at least partially control or compensate for potential underdevelopment and/or ghosting issues.
With at least some general aspects of operation of the exposure adjustment manager 300 in mind, more specific examples of implementing an exposure adjustment factor will be described. In some examples, decisions regarding application of an exposure adjustment factor are made via a pixel-by-pixel analysis per pixel-by-pixel parameter 370, as shown in
For illustrative purposes, some examples will be described with regard to underdevelopment related to prolonged non-development of at least some portions of the development element, and the associated overcharging of marking agent on development element 33. However, it will be understood that at least some of substantially the same principles may be applied to some examples regarding overdevelopment due to undercharged marking agent on development element 33 related to high marking agent transfer demands forced by high pixel density regions of an intended image.
For instance, when printing starts, the exposure system associated with light source 22 uses image information 20 (
In some examples, a magnitude of the adjustment of the exposure for the to-be-written pixel also is at least partially based on the values of excessive charged marking agent for each surrounding pixel (e.g. a 4×4 sample). In some examples, a different magnitude adjustment is made depending on whether a solid area (of which the pixel forms a part) is being exposed, a single pixel is being exposed, or half-toned areas are being exposed. After the to-be-written pixel is released (via control portion 28 in
It will be further understood that non-developed areas of marking agent on development element 33 pick up additional charge on each rotation of the roller 33. Accordingly, in some examples, this phenomenon is tracked to increase the accuracy of tracking the excess charge level on development element 33, and thereby increase the accuracy of the exposure adjustment factor. Accordingly, in some examples, a memory (e.g. 170 in
It will be understood that these examples of memory size are illustrative and not limiting, as the memory size may depend on the size and/or shape of the development element 33 as well as other factors.
With at least some examples employing a pixel-by-pixel exposure adjustment, the phenomenon of underdevelopment of image portions (e.g. segment 188B in
Moreover, in one aspect, at least some examples of the present disclosure may minimize underdevelopment and/or subsequent ghosting without unnecessarily wasting marking agent as would otherwise occur upon purging excess charged marking agent into an interpage gap of each page of a print job.
Accordingly, at least some examples of the present disclosure may reduce operating costs for the customer by saving marking agent. Moreover, by foregoing such purging activity, at least some examples of the present disclosure may enable use of a much smaller interpage gap, which in turn allows for higher effective print speed without speeding up the actual paper speed or the speed of any of the electrophotographic imaging process components. This, in turn, may prolong the life of all of the electromechanical parts of the electrophotographic imaging system.
In addition, by enabling use of a smaller interpage gap, at least some examples of the present disclosure solution may decrease the energy consumption involved in printing at a higher effective print speed because the physical space between each page is smaller for a given print speed. In addition, less “idle” time occurs in situations in which the print process is in operation but nothing is being printed on a page.
With at least some examples employing a pixel-by-pixel exposure adjustment, the phenomenon of overdevelopment of image portions (e.g. segment 269B in
In general terms, controller 382 of control portion 380 comprises at least one processor 383 and associated memories. The controller 382 is electrically couplable to, and in communication with, memory 384 to generate control signals to direct operation of at least some components of the systems, components, and modules described throughout the present disclosure. In some examples, these generated control signals include, but are not limited to, employing exposure adjustment manager 385 stored in memory 384 to manage unintentional underdevelopment, unintentional overdevelopment, and/or related ghosting for an electrophotographic imager in the manner described in at least some examples of the present disclosure. It will be further understood that control portion 380 (or another control portion) may also be employed to operate general functions of an electrophotographic imager. In some examples, exposure adjustment manager 385 comprises at least some of substantially the same features as exposure adjustment manager 300, as previously described in association with at least
In response to or based upon commands received via a user interface (e.g. user interface 386 in
For purposes of this application, in reference to the controller 382, the term “processor” shall mean a presently developed or future developed processor (or processing resources) that executes sequences of machine readable instructions contained in a memory. In some examples, execution of the sequences of machine readable instructions, such as those provided via memory 384 of control portion 380 cause the processor to perform actions, such as operating controller 382 to implement an exposure adjustment factor, as generally described in (or consistent with) at least some examples of the present disclosure. The machine readable instructions may be loaded in a random access memory (RAM) for execution by the processor from their stored location in a read only memory (ROM), a mass storage device, or some other persistent storage (e.g., non-transitory tangible medium or non-volatile tangible medium, as represented by memory 384. In some examples, memory 384 comprises a computer readable tangible medium providing non-volatile storage of the machine readable instructions executable by a process of controller 382. In other examples, hard wired circuitry may be used in place of or in combination with machine readable instructions to implement the functions described. For example, controller 382 may be embodied as part of at least one application-specific integrated circuit (ASIC). In at least some examples, the controller 382 is not limited to any specific combination of hardware circuitry and machine readable instructions, nor limited to any particular source for the machine readable instructions executed by the controller 382.
In some examples, user interface 386 comprises a user interface or other display that provides for the simultaneous display, activation, and/or operation of at least some of the various components, modules, functions, parameters, features, and attributes of control portion 380 and/or the various aspects of an electrophotographic imager, as described throughout the present disclosure. In some examples, at least some portions or aspects of the user interface 486 are provided via a graphical user interface (GUI). In some examples, as shown in
In some examples, the example of
As shown in
Like the example in
In some examples, the height (H2) of each segment 510A corresponds to a circumference of the development element 33, which is represented by H1 in
In this scenario, if the intended image portion 502A were actually developed without an exposure adjustment, then portion 502B in
In this example, segment 530E includes the surrounding non-print portion 522B (which surrounds upper star portion 520B and lower star portion 520C), which still corresponds to a non-developed portion of the development element 33 (
As represented by the relatively denser portion of cross-hatching in
In some examples, additional underdeveloped segments may occur subsequent to segment 5503 in which another “star-surrounding” portion would appear as an underdeveloped portion within the otherwise fully developed high pixel density region 5123.
In some examples, just one underdeveloped segment 540B (including “star-surrounding” portion 542B) is present without a second underdeveloped segment 550B (including star portion 550C and “star-surrounding” portion 552B). This situation may arise where the non-development of a portion of the development roller 33 is not as severe and/or where the high pixel density region of the intended image is less dense.
With this in mind, at least some examples of the present disclosure overcome the phenomenon that would be otherwise be exhibited by the underdeveloped image portion 502B via selectively applying an exposure adjustment factor 24 (
Employment of the exposure adjustment factor will compensate for the prolonged non-development state of portions of the development element 33 and thereby avoid the underdevelopment that would otherwise be exhibited in segment 515B (as portion 516B, and as upper star portion 520B), in segment 540B (as “star-surrounding” portion 542B), and in segment 550B (as “star surrounding” portion 552B) in
When such exposure adjustment is implemented according to at least some examples of the present disclosure, then the electrophotographic imager avoids producing an underdeveloped print segment 515B (including portions 516B, 520B), underdeveloped segment 540B (including “star-surrounding” portion 542B), and underdeveloped segment 550B (as “star-surrounding” portion 552B) in
As noted in connection with
In a manner similar to the examples of
However, unlike the prior examples of
Segment 604B is followed by a subsequent segment 610B having a “text-surrounding” portion 611B (the areas surrounding the printed text characters) which appears as an underdeveloped image in a region which should appear as a relatively uniform high pixel density segment 610A.
In particular, the “text-surrounding” portion 611B in segment 610B corresponds to an initial development instance for high pixel density segment 610A that follows the last iteration/Instance of the non-developed portion 605A, which surrounds the text characters in segment 604A. In some examples, the “text-surrounding” portion 611B immediately follows the last iteration/instance of the non-developed portion 605A.
In one aspect, the underdevelopment of the text-surrounding portion 611B results in a ghost of the text characters of the segment 604B in the at least the sense that the text characters from segment 604B make an unintended and undesired appearance in at least segment 610B.
As further shown in
As in the prior examples of
As shown in
At 708, method 701 includes arranging a development element to be coupled relative to the photoconductive element to develop the latent image on the photoconductive element with a marking agent (e.g. toner). In one aspect, at least the first exposure adjustment factor is based at least on a magnitude of a pixel density of a first evaluation portion of the latent image preceding the first printable area and a development state of the development element. In some examples, the first evaluation portion immediately precedes the first printable area. In some examples, at least the second exposure adjustment factor also is based at least on a magnitude of a pixel density of a first evaluation portion of the latent image preceding the first printable area and a development state of the development element. In some examples, the first evaluation portion immediately precedes the first printable area.
At least some examples of the present disclosure provide for electrophotographic imaging with reduced underdevelopment, reduced overdevelopment, and/or ghosting effects by employing an exposure adjustment factor.
Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.
Hirst, Mark, Shaw, Mark, Larson, Brad
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Jul 28 2015 | HIRST, MARK | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 044834 | /0948 | |
Jul 28 2015 | LARSON, BRAD | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 044834 | /0948 | |
Jul 29 2015 | SHAW, MARK | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 044834 | /0948 | |
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